Evaluation of heating capacity of shallow ground heat exchangers in different Locations– A case study of two administrative districts of Xi'an

Abstract

As a case study, two administrative districts of Xi'an are selected. Eight sites are drilled for shallow ground heat exchangers (SGHEs), and thermal response tests (TRTs) are conducted on the ground to investigate the heating capacity of SGHEs in different locations. The vertical distribution of initial ground temperature is identified using a temperature sensing system in TRTs. Simultaneously, the real-time inlet and outlet water temperatures of SGHEs are monitored by controlling heating power and buried pipe flow rate to be constant, and the thermophysical parameters of the ground are derived. A three-dimensional full-scale numerical model for buried pipe heat transfer is developed based on the results of TRTs. The heating capacity distribution of SGHEs is determined by clarifying the characteristics of buried pipe heat transfer at various locations and depths. The results showed that the maximum difference in geothermal gradient and ground thermal conductivity is 51.2 °C/km and 0.51 W/(m·K) respectively, indicating that the ground parameters vary significantly within the chosen places. The heat transfer intensity of SGHEs is directly related to buried pipe depth and mean circulating water temperature at the same locations. The same prediction formula can describe the heat transfer intensity of SGHEs at various locations.